1. Field of the Invention
The present invention relates to an electric compressor in which an electric motor portion and a compressor portion are integrated and, in particular, to an electric compressor in which a drive circuit portion for supplying electric power to the electric motor portion is integrated with the compressor portion.
2. Description of the Related Art
Attempts have been made to integrate a refrigerant compressor, for an air-conditioning system mounted in an automobiles, with an electric motor for rotatably driving the refrigerant compressor via a common rotating shaft, and to integrate a drive circuit portion, such as an inverter for supplying power to the electric motor, with the electric motor, in order to reduce the amount of wasted space and the size and weight of the overall structure, by using, in conjunction, as many components as possible, to facilitate installation of the compressor in a vehicle where there is not enough space, to simplify the arrangement of the transmission shaft, wiring, piping and the like linking the various components, and to reduce the cost.
When integrating a refrigerant compressor and electric motor in this way, as a means for cooling the electric motor, in which overheating is a problem due to the density of installation, a method of guiding a low temperature intake refrigerant, consisting mainly of gas returning to the refrigerant compressor from the evaporator during the refrigeration cycle, and cooling the inside of the electric motor by circulating this gas through the electric motor, can be performed. For this purpose, in the prior art, a passage for circulating the intake refrigerant, formed between the stator of the electric motor and the housing enclosing this, is normally provided uniformly surrounding the rotating shaft of the electric motor.
Consequently, where a heat radiating body such as a drive circuit portion including an inverter is integrated with part of the periphery of the housing of the electric motor and with other heat radiating bodies disposed in proximity thereto, due to heat emitted from the heat radiating bodies of the drive circuit portion and the like, part of the electric motor attached or in proximity thereto suffers from a localized rise in temperature because it cannot be sufficiently cooled, the temperature around the rotating shaft of the electric motor becomes non-uniform, and oscillation problems or the like occur due to differences in the minute space between the stator and armature as a result of localized heat expansion differences, resulting in a non-uniform magnetic field being generated by the stator and rotational imbalance, thus reducing efficiency. Also, because the drive circuit components such as the inverter and the like are not sufficiently cooled by indirect cooling alone from the inside of the electric motor by means of intake refrigerants returning to the compressor, there is a problem of a reduction in the durability of the drive circuit components.